Vacuum vaporization-condensation cooling system



A ril 14, 1953 M. w. BEARDSLEY 2,634,592

VACUUM VAPORIZATION-CONDENSATION COOLING SYSTEM Filed 001:. 10. 1950INVENTOR. MEL was 14 55400315? Patented Apr. 14, 1953 UNITED STATE PTENTQFFICE VACUUM VAPORIZATION- CONDENSATION COOLING SYSTEM Claims.

My invention relates generally to the cooling and refrigeration ofcomestibles, and more particularly, to the pre-cooling of such produceas lettuce,-sweet corn, prior to its shipment. A method and apparatusfor this general purpose are disclosed in my co-pending application,Serial No. 146,784, filed February 28, 1950, and entitled Method andMeans for Cooling Produce by Use of Reduced Pressures, of, which thepresent application is a continuation-in-part.

One customary practice in cooling produce such as lettuce prior to andduring shipment thereof is to interlayer the produce with crushed icewhile it is being packed into the shipping crates, and also to cover theclosed crates with ice in the refrigeration cars in which they areshipped. As stated in the above-identified co-pending application, thedisadvantages of the conventional procedure just described are that thecrushed ice tends to bruise tender vegetables such as lettuce; the waterfrom the melting crushed ice causes considerable deterioration anddiscoloration of the produce during shipment thereof, and is generally anuisance; and the crushed ice, in spite of great care in distribution,does not maintain as uniform a temperaure throughout the body of thepacked shipment as is desired. Still further, the operation of packingthe crushed ice into crates or other containers with the produce is acostly and time-consuming phase of the packing and shipping operation.

The above-identified co-pending application discloses a method and meansfor precooling produce by means of a vacuum causing evaporation of thesurface moisture therefrom, a process described generally as vacuumcooling. The present invention concerns further improvements in themethod and apparatus for vacuum cooling. In current practice, the vacuumcooling process employs steam jet pumps to evacuate the air and watervapor from a closed chamber containing-the produce in process. Steam jetpumps have proven more satisfactory for this Bearing in mind the generalpurposes of vacuum pre-cooling and also the fact that steam+ operatedplants currently in use are of a permanent type, it is a major object ofthe present invention to provide a light-weight, portable, vacuumpre-cooling plant adapted especially for use with seasonal produce suchas lettuce.

Another object 01 the invention is to reduce the size and expense ofvacuum pre-cooling plants even of the permanent installation type.

A further object of the invention is to provide for the use of ice inconnection with the'process of vacuum cooling, and also for a minimum ofhandling of such ice without the necessity of placingv the same indirect contact with the produce being cooled.

Yet another object of the invention is to provide a system adapted forthe use of mechanical refrigeration in connection with the vacuumcooling process.

A still further object is to reduce the power requirement of a vacuumcooling plant.

An additional object is to increase the speed and facility with whichproduce may be precooled by the vacuum cooling method.

Yet another object is to provide a vacuum cooling plant in which therefrigeration and vapor condensing unit is separate from and readilydetachable from the main produce-containing chamber, whereby thecondensation unit may be used successively with a number of differentproduce-containing chambers.

A still further and general object is to provide apparatus formaterially increasing the speed and efficiency of ice refrigeration fromthe standpoint of the theoretical absorption capacity of the ice.

Yet another object is to provide in a vacuum cooling system, efficientmeans for removing water in an ice-vacuum cooling refrigeration system,efiicient means for. removing water from the refrigerating chamberwithout wetting the produce.

The foregoing and additional objects and advantages of the inventionWill be apparent from a consideration of the following detaileddescription of several forms thereof, such consideration being givenlikewise to the attached drawings, in which:

Figure 1 is a side elevational view of a presently preferred form of theinvention using ice, and in a which a pump and refrigerated condensationunit is mounted on the tractor portion of a trucktrai1er combination,and in which a produce-containing, cooling chamber trailer portion;

is mounted on the Figure 2 is an enlarged elevational longitudinalsection taken through the condensation and treatment chambers of theapparatus shown in Figure 1;

Figure 3 is an enlarged elevational section taken through a modifiedform of condensation chamber in which refrigerating coils are employedin place of the ice shown in Figure 2; and

Figure 4 is a further modified form of the invention employing anexternal ice bunker in place of the internal ice bunker of the apparatusshown in Figure 2.

Briefly, the apparatus employing my invention comprises a mainproduce-conta ning chamber H and a vapor-condensing chamber [5, the twochambers being interconnected by means of a flexible conduit having aquick-disconnect joint or fitting 27 therein. Incorporated in thecondensin chamber unit is a vacuum pump 29-- and a cold body to effectcondensation of moisture, such body'be'ing, for example, the ice I!shown -in Figure 2, or mechanical refrigeration cold coils-35 in theform shown in Figure 3.

The'quick-operating connection joint 2'! provided in the interconnectingconduit 15 provides for the successive connection of the condensationchamber [5 with a number of different main chambers H.

Before proceeding with a detailed description ;.of the apparatusembodying the present invention, the principles of operation will bedescribed briefly-as follows. The first principle made use of is thatevaporating -moisture absorbs heat of evaporation from surroundingmedia. Thus, if the surface moisture on, let us say, a head of lettuceis caused to evaporate by reducing the surrounding vapor pressure, theheat of evaporation necessary to cause the same will be absorbed fromthe head of lettuce, thus cooling the same. .Thisprinciple-is alsoemployed in the apparatus described in theabove-identified co-pendingapplication.

The second principle employed in the present invention is that vaporbrought intocontact with a surface colder than the dew point of suchvapor at its then pressure will cause the vapor to condense vwith theresult that a corresponding amount of heat is released by the vapor andabsorbed by the. cold surface. Such condensation 'also of course,results in reduction of pressure ifit is accomplished in a closedchamber.

The third. principle employed herein is that the vapor pressure of agiven liquid depends on the" temperature thereof; thus, if two vesselsv.Qcont'aining separate bodies of the, same liquid at 'difier'enttemperatures are interconnected and all air and other non-condensablegases are removed, vapor of the liquid will flow from the vessel ofhigher temperature to the vessel of lower temperature because of thehigher vapor pressure of the higher temperature liquid.

These three general principles are employed in the present apparatus byplacing in one chamher the material to be cooled and in the connectedchamber, means for maintaining a low temperature; and then removing theair and noncond'ensable gases from the two interconnected chambers. Itwill be apparent that, as the air ,and non-condensable gases areremoved, the 'pressure in the two chambers will ultimately be reduced toa value equal to the vapor pressure of the surface moisture present onthe produce. At this point, the absolute pressure in the condensingchamber is approximately equal to the vapor pressure of the surfacemoisture, but according to Avogadrcs law, it is comprised of the lowervapor pressure of the colder moisture (or ice) plus the partial vaporpressure of the air and non-condensable gases which are also present. Asair is continuously removed from the condensing chamber, the totalpressure therein will be reduced until, when all air and othernon-condensable gases are removed, the total condensing chamber pressurewill become equal to the vapor pressure of the colder condensate or ice.

Under the conditions last above described, vapor will flow at highvelocity from the main chamber to the condensing chamber. The vaporcontinues to be boiled off the produce and to flow into the condensingchamber until the vapor pressurein both chambers is substantially equal.This condition of equality, of physical necessity, means that thesurface moisture on the produce has been reduced to the same temperatureas the moisture or ice in the condensing chamber. For leafy produce suchas lettuce, this is tantamount to a reduction to this temperature. ofthe entire, mass of the produce. Thus, in summation, it is seen that thevacuum cooling process consists in removing heat from the produce andtransmitting the same to ice or other refrigerant through the medium ofevaporated and recondensed vapor.

From the preceding discussion, it will be seen that when the air hasbeen substantially removed from the two chambers, there is theoreticallyno need for further evacuation. I' have found by experience, however,that there is still a substantial amount of air present in thechambers'by the time the point of rapid evaporation and flow of watervapor commences therein. In addition to the condition just stated, theremay be a slight amount of air leakage in the chambers, and furthermore,non-condensable gases, such as carbon'dioxide, are given off by theproduce being treated. Thus, I have found it necessary and desirable tocontinue the evacuation,

though at a reduced rate, throughout the process in order that thecooling will continue at a maximum rate.

Whenever any small amount of air or other non-condensable gas is presentin the condensing chamber, it will, according to Avogadros lawabove-mentioned, add its partial pressure to that of the vapor pressureof the condensate, so that the total may be great enough to equal thevapor pressure of the surface moisture on the produce, and thus stop theentire process. Furthermore, if any air is allowed to remain in thecondensing chamber, even though the partial pressure thereof may not besufiicient, theoretically, to halt op erations, it soon collects in aninsulating blanket on the ice or other condensingsurface and prevents orgreatly inhibits further condensation. The formation of such a blanketis due to the fact that the condensation at the cold surface removes thewater from the air-water-Vapor mixture thereat, leaving relatively pureair. Thus, it is of further advantage to continue the pumping during theentire cooling cycle in order to keep the aforesaid blanket of air fromforming and to continuously draw water vapor into contact with thecondensation surface.

In the preferred form of the apparatus illustrated in Figure 1, the mainchamber I! is charged with produce while the connected condensationchamber I5 is charged with ice. The

chambers are thereafter substantially evacuated of air, the heattransfer starts automatically and is allowed to continue until theidesir'edfpr'ecooling temperature of the produce has been reached. a

An important feature of the present process is that substantially nowork or energy is expended in pumping vapor out of the main chambercontaining the material being processed, substantially the only materialremoved therefrom being air.

It will be realized that this is a major advantage of the presentequipment over apparatus employing steam jet pumps and continuing thepumping operation to reduce the vapor pressure in the treatment chamber.In the latter type of apparatus, the major portion of all the energyrequired is used in pumping water vapor out of the treatment chamber.

As described in my above-mentioned co-pending application, I have foundit possible to closely calculate the amount of ice required to produce agiven reduction in temperature in a given weight of produce. Experiencehas shown, however, that often an undesirable amount of time and laboris required to load the chamber with a calculated amount of ice.Furthermore, it is usual practice to provide a safety factor by placingin the condensing chamber slight y more ice than the theoretical amountnecessary to produce the desired cooling effect. Thus, there is aresiduum of ice after the process has been completed which must usuallybe disposed of because it is of odd'and undesirable shape for optimumoperation.

As a means of reducing this labor and undesirable ice residuum, I havefound is desirable to make the condensing chamber sufiiciently large tocontain enough ice for cooling several loads of produce; thus, the icecan be loaded relatively infrequenly and without regard to the exactamount needed to pre-cool any particular load of produce.

As a means of accelerating the cooling process, particularly toward theend of a cycle, I have found it expedient to spray on the cold surfacein the condensing chamber a chemical solution which lowers the meltingtemperature of ice and also reduces the vapor pressure of condensateformed therein.

Referring now to Figure l for a more detailed description of thepreferred form of apparatus embodying the Jresent invention, it will beseen that the treatment chamber II is of cylindrical configuration,having a hinged access door I3 formed in one end thereof, and a simplecircular bulkhead closing the other end. The cham er II is mounted on atrailer 5i which is adapted to be towed by a truck 5G carrying-thecondensation chamber I5 and the vacuum pump 20, together with otherrefrigeration equipment. During the time that the cooling process is inoperation, the main chamber II is connected to the condensation chamberI5 through the interconnecting conduit I6 having the quick-disconnectjoint 27 therein. The interconnecting conduit I6, while adapted towithstand external atmospheric pressure when the interior thereof issubstantially evacuated, is made flexible in order to facilitateoperation of'the joint 21 and also to permit operation of thetruck-trailer 5il5l while the cooling process is continuing.

A'valve Ita is incorporated in the interconnecting line I6 and manuallyoperable to close the chamber II so that the vacuum therein may be-m'aintained even thou h the chamber II is disconnected from thecondensing chamber I5. --As seen best in Figure 2, a series of conveyorrollers I 4 is mounted in the chamber I I to receive crated produce formovement into the chamber in conventional roller conveyor manner. Aflow-directing baffie 38 is installed under the conveyor rollers I4,extends completely across and throughout the length of the chamber II,except for a small gap adjacent the access door I3, and serves toestablish a uniform vapor flow path out of the chamber II, a indicatedby the flow arrows in Figure'2.

At the top of the condensing chamber I5 is a hinged and sealed bulkheadtype door I9 through which ice I! may be loaded into an internal icecompartment 30 within the chamber I5. The ice compartment 30 is formedwith a heat-conducting inner wall I8, having a sloping bottom so as toslide the ice forwardly against the for.- ward wall of the chamber I5.

A vacuum pumplll is connected by a suction line 2| to the interior ofthe chamber I5 adjacent the lowest point in the ice compartment 30. At

the lowermost point in the compartment 30, a

condensate drain pipe 24 serves to drain away condensate and. meltedice'to a, condensate tank 23 which may be conveniently mounted at anypoint substantially below the lowermost point in the chamber I5. An airinlet valve 45 is connected in the suction line 2|, and is selectivelyoperable to admit air to the system after completion of the coolingcycle.

The system illustrated in Figure 2 operates as follows. After the ice I!and the produce in crates I2 have been loaded into the respectivechambers I5 and II, and the doors I3 and I9 have been closed, anair-tight system containing the ice I1 and produce crates I2 at ambienttemperature is established. Air is then pumped out of the system bymeans of the pump 20 through the conduit 2|, the inner end of which isconnected to a series of laterally disposed exit ports 28 in the innerwall of the ice compartment 30 adjacent the bottom thereof. By thisarrangement all gas, whether air or water vapor, which is removed fromthe interior of the cooling chamber I I, must pass through thecondensing chamber I5 and the inner ice compartment 30 in closeproximity to the surface of the blocks of ice I! therein. The watervapor constituent of the moving gas mixture is largely removed bycondensation of the ice I I, thus making it necessary for the pump tomove only substantially pure air. This, in turn, makes possible the useof a pump of relatively small volumetric capacity, as compared withvacuum cooling systems which operate by pumping out all gases includingevaporated water vapor.

When the total pressure in the cooling chamber II and in the condensingchamber I5 is equal to or slightly greater than the vapor pressure ofthe moisture on the produce, then the system is in equilibrium and willremain so if the pumping is discontinued. However, if the pumping iscontinued past the point where the system total pressure is equal to thevapor pressure of the produce moisture, then boiling of the producesurface moisture occurs. This boiling will continue until the vaporpressure of the moisture in the cooling chamber I I-is equal to thetotal pressure in the condensing chamber I5. Thus, if all air andnon-condensable vapors are removed from the condensing chamber I5, thetotal pressure therein will be that corresponding to the moisture on thesurface of the ice. Therefore, moisture in the cooling chamber II willcontinue to evaporate until the moisture tem- =perature in the same-isthe same as the moisture on the surface of the ice [1, and the-condensinchamber 15.

During the cooling process, the vapor formed by the evaporation. of theproduce surface moisture flows into the condensing chamber through theinterconnecting conduit 15, and is caused: by a deflecting baffle 29' toimpinge on a. sloping heat transfer surface 26 down which is flowingwater consisting of melted ice and condensate.

Since this water flowing down the surface of the sloping wallZE has. atemperature of approximately 32 degrees, it causes condensation of asubstantial proportion of the water vapor impinging: against theundersurface and absorbs heat therefrom. Thus, the mixture of condensateand melting ice approaches the temperature of the vapor impinging uponthe wall 28 as such liquid mixture leaves the compartment 35 through thedrain pipe 2 That portion of the vapor which is not con- "densed byimpingement against the heat ex- ."change surface 26 passes, asindicated by flow arrows, around the substantially horizontal baffle 29and along the outer surface of the ice compartment wall l8, up to thetop of the ice compartment 39 where it comes in direct contact with theice II. Since the vacuum pump 29 is continuously operating, any air ornon-condensable gas that is mixed with the vapor will be drawn throughthe ice-containing chamber "30, and out through theexit ports 23 afterpassing in intimate heat transfer contact with the ice II so thatsubstantially all vapor is condensed.

As the ice i1 is melted by the released latent heat of evaporation, themelted ice and condensate drains, as aforesaid, to the bottom of the icecompartment 39 and out through a series of laterally disposed draintubes 3| into an inner drain reservoir 33. When this small reservoir 33is full, the liquid therein overflows and down the sloping bottomsurface 26, as described. This system of drain tubes 31 and thereservoir 33 serves as a trap at the bottom of the ice compartment 39 sothat the vapor must follow the flow path previously described andtherefore enter the ice compartment as at the top and pass downwardlytherethrough. In this way, maximum condensation effect is achieved.

In this connection, I have found that, as compared to other flowdirections, a generally downward flow path over the ice, or other coldcondensating surface, is of considerable advantage andefiects-aconsiderable improvement in efficiency since air, being more dense thanwater vapor, will tend to flow naturally to the bottom of the chambercontaining the condensation surface, into the discharge ports 28, andthence to 'the vacuum pump. 11?, on the contrary, the flow of vapor-airmixture were to be upward past the condensing surface, the air wouldtend to form an insulating blanket against the surfaces, since the lightwater vapor constituent tends to rise and the heavier air constituenttends to slide down "along the cold surface counter to the flowdirection, thus preventing eflicient vapor condensation of ice surfacetemperature and vapor pressure is accomplished in the present instanceby injecting a solution containing a chemical such as common salt orcalcium chloride against the ice surface. For this purpose, in thepresent embodiment a solution tank 34 is provided and con-'- nected by asuitably valved conduit 39' to the interior of the ice compartment 30 sothat by operation of the valve 35a in the conduit 36, solution issprayed through a set of interior nozzles 35 onto the ice I1.

Efhciency of the system is also greatly improved by covering thecondensing chamber IS with a layer of insulating material 31 in orderthat heat will not be absorbed from atmosphere.

Such insulation is particularly necessary on the sloping heat transfersurface 26 to prevent the melted ice and condensate mixture fromabsorbing heat and increasing its vapor pressure, thus reducing overallefficiency. Unless the vapor pressure of all liquids in the chamber I5is maintained as low as possible, the final desired temperature may notbe reached, even though pumping is'continued and all of the iceconsumed.

An alternate form of the invention is illustrated in Figure 3 whereincold coils 39 of a mechanical refrigeration system of known design areemployed instead of ice in the condensirig chamber It. In this modifiedform, refrigerating coilste of a conventional mechanical refrigeratorare mounted in heat transfer contact with the bottom surfaces of anumber of horizontally disposed condensate trays 45.

A compartment 39a, analogous to the ice compartinent 39, of the previousembodiment, is provided in the form shown in Figure 3, and the trays itare staggered and spaced vertically in the compartment 39a so as to actas baffles and provide a tortuous downward path for vapors passingthrough the compartment. vThis arrangement causes the air and watervapor mixture moving through the condensing chamber [5 to sweep in closecontact with both the upper and lower surfaces of the trays 49, and thecoils 39 secured to the undersurfaces thereof. The refrigerationequipment necessary to supply cold refrigerant to the coils 39 is ofconventional design and need not be described in detail herein. Such amechanical refrigeration plant can be mounted on the tractor 59 andpowered either by the prime mover of the tractor itself, or by asuitable auxiliary power plant.

The operation of the modified form shown in Figure 3 is similar to thatof the previously described embodiments. Vapor fiows from the mainchamber I I through the interconnecting conduit it into the condensingchamber I5 and is deflected by a baffle 29 to impinge on the slopingliquid-heat transfer surface 26. Uncondensed vapor and any entrained airleaving the surface 28 flows upwardly, as indicated by the flow arrowsin Figure 3, to the top of the compartment [5 and thence downwardly overthe coils 39 and their adjacent trays :19 to discharge ports 52, thenceinto the suction line 2| leading to the vacuum pump 20. Condensate fromthe vapor condensing on thecoils 39 drips downwardly into the trays 49until these are filled to the level of an overflow tube in each,identified by the reference character 4!. After reaching this level,additional condensate runs out of the overflow tubes 4! into smallsealing reservoirs or traps 10 located at the ends of each of the tubes4| and mounted to the wall I80. of the inner chamber 39a. When thereservoirs 10 are filled with condensate,.the

sameyoverfiows and drops downwardly to the sloping heat exchange surface26 and out the condensate drain pipe 24.

The purpose of the condensate trays 40 is to retain a substantial massof liquid condensate so that it may be frozen into ice by therefrigerating coils 39 during the period in which the main chamber H isbeingunloaded and reloaded with additional produce for the next cycle.By this means, the refrigerating plant supplying the coils 39 can beoperated continuously, the trays 40 and the frozen condensate thereinserving as a heat absorbing ballast and thus building up the,

heat absorbing capacity of the system. This arrangement makes possiblethe use of a comparatively smaller refrigerating plant (for a given rateof cooling) than would be required if all the heat of vapor condensationwere absorbed directly by the refrigerating coils during the initialpart of the cooling cycle. The same general result can be accomplishedby spraying water over the refrigerating coils during the loadingperiod. This water, if sprayed at the proper rate, will form ice on therefrigerating coils and thus build up heat absorbing capacity as setforth above.

When refrigeration coils are employed, as shown in Figure 3, the flowpath of air and vapor mightbecome blocked because of the accumulationofice on the coils, particularly on the coils adjacent the discharge ports42. This is particularly true when a counterflow system is employed inwhich the refrigerant enters the coils at the end adjacent the ports 42.

-As a means'of preventing the aforesaid blocking of flow due to theformation of ice, -I have found it expedient to provide a flexible flapor 'membrane 43 mounted so that its free edge rests on a transverselength 390. of the refrigerating coils 39 immediately adjacent thedischarge ports 42. With this arrangement, when the ice formation blocksthe normal flow path, the suction created in the vacuum line 25 liftsthis membrane 43 sufficiently to permit the continued flow of air andvapor out of the discharge ports 42, such continuous flow passing inintimate contact with the aforesaid coil length 39a.

Additional, or in some cases alternative means are provided forpreventing the blocking of flow by the formation of ice, such additionalmeans being a nozzle 44 mounted adjacent the port 42 and adapted tospray a chemical solution of freezing point lowering material such ascalcium chloride whereby to melt the accumulated ice and unblock theflow. The addition of such a chemical solution also has the favorableeffect of reducing the vapor pressure of the condensate contained in thecondensate pan 4%) immediately below the exit port #2.

In the embodiment illustrated in Figure 4, the released latent heat ofevaporation is removed fromthe condensation chamber by conductionthrough the walls themselves. To porduce this effect, the condensationchamber [5a is cylindrical in form and a portion of the outer surface iscooled by the application of ice I? thereagainst, the ice being supprtedin an external bunker H. In the operation of this embodiment, vaporenters the condensation chamber 15a through the interconnecting conduitl5 and is deflected by the bafile 29 in the manner of the previousembodiments. Thus, the incoming air-vapor mixture is caused .to followtheinner wall surface of the chamber 15, as indicated by the flowarrows. As thevapor flow follows the refrigerated surface, the vaporcondenses and the condensate drains to the bottom of the chamber l5dwhere it is removed through the drain pipe 240., in the man-.

ner previously described. Any air or non-condensable gas mixed with thevapor is carried on around the wall surface to the laterally spaced exitports 28a, and leaves the chamber in the manner previously described.

As the heat of vaporization from thecondensmg vapor is conducted throughthe wall of the chamber 15a, the ice I1 is melted and the resultantwater drains down into a liquid flow space 52 between the bunker H andthe chamber l5a. In the space 52, th melted ice-water is 0 strained toflow along the exterior surface of the condensing chamber Walls so thatan additional heat transfer is effected between the condensing vapor andthe melted ice-water. maximum refrigerating efliciency is obtained sincethe melted ice-water is heated to nearly the same temperature as theentering vapor before it finally leaves the system through anoverflowice drain 53.

A nozzle 54 serves to introduce a melting point reducing solution intothe contact surface between the exterior surface of the chamber 15a andthe ice ll, thus reducing the temperature at this point.

In order to achieve a maximum possible rate of cooling, I have found itdesirable and expedient to incorporate within the condensation chamber.

15a (or in the chamber [5 of the previous forms) a blower 55 whichincreases the rate of condensation on the inner chamber wall surface.The blower 55 is arranged to discharge onto the inner wall surface, asindicated in Figure 4. The increased velocity of surface flow and theturbulence created by this blower increase the rate of condensation,both by removal of the aforementioned air blanket that tends to form onthe condensing surface, and also by agitating and moving the condensedwater so that the uncondensed vapor obtains more direct contact with thecold wall surface.

In all of the embodiments illustrated, airis admitted to the systemafter the desired precooling temperature is reached by means of the. airinlet valve 45 connected to the end of thepump suction line 2|. All ofthe illustrated embodiments employ the same method and means for dumpingthe condensate drain tank 23 at the.

end of the pre-cooling cycle. Referring to Figure 2, it will be seenthat a condensate tank discharge valve plug 25 is attached to one end ofa pivoted lever 60 which is supported on a pin joint BI, and has acounterweight E3 thereon on the opposite side of the pin 6! from thevalve plug 25. A metal actuating bellows 64 is connected at one end tothe lever arm 86 and at the other end to a fixed portion of thestructure. tuating bellows 64 is communicated with the main suction line2! by a tube and a fitting 66.

Thus, when the vacuum pump 20 is started at the beginning of anyparticular cooling cycle, the pressure in the actuating bellows 64 isreduced, causing the same to contract under the influence of atmosphericpressure. Such contraction of the bellows 6d raises the valve plug 25into the adjacent discharge valve seat. When seated, the.

valve is further held shut by the action ofatmospheric pressure thereon,and no leakage occurs at this point. Weight 63 is so adjusted that onlya small force need be exerted by the bellows 64 to close the plug 25 asaforesaid. When air is readmitted to the system and thus also to thebellows 64, it and the By this means,

The interior of the ac-.

lhe position of the counter 11 weight of the water above the plug 25cause the valve to open, dumping the contents of the condensate tank 23.

It will be noted that in all of the forms illustrated the flow throughthe condensation chamber is so organized that air-vapor passingtherethrough must pass in heat transfer relation with the coldcondensation surface before reaching the exit ports. Also bafile meansare provided in each case to prevent any substantial body of condensatewater from being located immediately adjacent the exit ports. Thiscreates a condition of optimum efficiency in that relatively greatproportions of air are moved by the pump as compared to the vapor movedthereby.

While the forms shown and described herein are fully capable ofachieving the objects and providing the advantages hereinbefore stated,they are capable of some modification without departing from the spiritof the invention. For this reason, I do not mean to be limited to theforms shown and described, but rather to the scope of the appendedclaims.

I claim:

1. In a vacuum cooling system of the class described: a hermeticenclosure having a scalable access door to receive material fortreatment in said enclosure; evacuation and condensation means includinga chamber having a cold surface therein, a vacuum pump connected to saidchambet to evacuate the same, and conduit means connected to saidenclosure to inter-communicate said'chamber and enclosure; and means todirect liquid condensate forming on said cold surface to a point in saidchamber adjacent the infiuxof vapor and air from said conduit meanswhereby the air-vapor mixture drawn from said enclosure through saidchamber first passes in heat transfer relation past said condensate andthen in contact with'said cold surface.

2. 'In a vacuum cooling system of the class described: a hermeticenclosure having a scalable access door to receive material fortreatment in said enclosure; evacuation and condensation means includinga chamber having'a cold surface therein, "a vacuum pump-connected tosaid cham ber to evacuate the same, and conduit 'means connected to saidenclosure to intercommunicate said chamber and enclosure; means todirect liquid condensate forming on said cold surface to a'point in saidchamber adjacent the influx of vapor and air from said conduit means;and baffle means'positioned between said influx and the point ofconnection of said vacuum pump and said chamber whereby air-vapormixture drawn from said enclosure through said'chamber first passes inheat transfer relation with said condensate and then in contact withsaid cold surface;

3. In a vacuum coolin system of the-class described: a hermeticenclosure having a scalable access "doorto receive material fortreatment'in said enclosure; a chamber communicated with said enclosure;a mechanical refrigerator having thecold coils thereof positioned insaid chamber; avacuum pump connected to said chamber to evacuate thesame and said enclosure; and reservoir means in said chamber to retainabody of 'water in heat transfer contact with'said coils whereby toprovide a heat absorbing ballast therein.

Ina vacuum cooling system of the class described: a hermetic enclosurehaving a'sealable access door'to receivematerial for treatment in saidenclosure; a'chamber communicated with 12 said enclosure; a mechanicalrefrigerator-having the cold coils thereof positioned-in saidchamber';

a vacuum pump connected to anexit port'insaid chamber to evacuate thesame and said-enclosure; and yieldable flow constricting means poshtioned adjacent said exit port of said chamber and adapted to constrainexiting gases to flowpast acoldest portion of said "coils, saidyieldable constricting means being adaptedto move tccpre= vent blockingof said exit port asice builds upon:

said coldest coil portion.

5. The method of vacuum coolingcomes'tibles having surface moisturethereon comprising the steps of: placing said material to be cooled in ahermetically sealed system; refrigerating aninterior surface of saidsystem; evacuating said'sys: tem; draining condensate from saidrefrigerated surface; and passing-watervapor from saidco mestibles inheat transfer relationfirst with said condensate and then downwardlypastsaid re frigerated surface.

I 6;- A ortable vacuum COOIiI-Tg plant'comprismg" in combinations atractor; a trailer connectedtd said tractor to bedrawn thereby; ahermetic enclosure mounted "on said trailer and having a rear accessdoor and conveyor means therein-to receive packed produce for treatmentin samenclosure; an insulated, hermetically scalable-chainber mountedon-said tractor having ah access door for loading ice into "saidchamber;adldxible conduit having a quick-disconnect-ioint therein; said conduitbeing connected be nsaidch'amher and enclosure to interccmmunicat'ethesamey an inner compartment in said chamberhaving an open top toreceive'said ice and comfnunicate said inner compartment with saidchamber; said inner compartment'having separate vapor and liquid exitports adjacent the bottom thereoi and said inner compartment having onevertical wall thereof spaced from a vertical wall of said chamberwhereby to form a vertical flue; a vacuum pump mounted on said tractorconnected to sai-d vapor exitports to withdraw air from theem closedsystem comprisin said i'nner ccm'part ment, chamber, and enclosure;water trap means in said liquid exit ports to preventccuntei-new ofvapor therethrough; an inclined inte'rior surface in said chamberbelow-said inner compartment to receive condensate an-d melted ice from-said liquid exit ports; and baflie-means in said chain'- her to directvapor'flowing into said chamber from said conduit in heat transfercontact against saidinclined surface -and thereaftei' up said fine toenter said-inner compartment "at said open top thereof.

7. In a vacuum cooling plant of thetype having a scalable enclosure toreceive material for treatment therein, means to evacuate-said enclosure and condense vapor withdrawn therefrom, comprising in combination:an insulated, hermetically scalable chamber havingan access door forloading ice into saidchamber; a flexible conduit having aquick-disconnect joint therein, said conduit being adapted'forconnection between said chamber and enclosure to 'intercommunicate thesame; an inner compartment insaid chamber havingan open top to'receivesaid ice :a'nd'communicate said inner compartment with 1 saidchamber, said inner compartment having separate vapor and liquid exitports adjacent' the bottom thereof, and said inner com artment h'av. ingone vertical wall thereof spaced froma verti cal wall of said chamber-whereby to form aver tical flue: a vacuum pump connected to said vaporexit ports to-"withdraw-air from-the err-- closed system comprising saidinner compartment, chamber, and enclosure; water trap means in saidliquid exit ports to prevent counterflow of vapor therethrough; aninclined interior surface in said chamber below said inner compartmentto receive condensate and melted ice from said liquid exit ports; andbaflie means in said chamber to direct vapor flowing into said chamberfrom said conduit in heat transfer contact against said inclined surfaceand thereafter up said flue to enter said inner compartment at said opentop thereof.

8. In a vacuum cooling plant of the type having a sealable enclosure toreceive material for treatment therein, means to evacuate said enclosureand condense vapor withdrawn therefrom, comprising in combination: aninsulated, hermetically sealed chamber; a flexible conduit having aquick-disconnect joint therein, said conduit being adapted forconnection between said chamber and enclosure to intercommunicate thesame; an inner compartment in said chamber having an open top tocommunicate said inner compartment with said chamber, said innercompartment having separate vapor and liquid exit ports adjacent thebottom thereof, and said inner compartment having one vertical wallthereof spaced from a vertical wall of said chamber whereby to form avertical flue; a vacuum pump connected to said vapor exit ports towithdraw air from the enclosed system comprising said inner compartment,chamber, and enclosure; water trap means in said liquid exit ports toprevent counterflow of vapor therethrough; an inclined interior surfacein said chamber below said inner compartment to receive condensate fromsaid liquid exit ports; and baflle means in said chamber to direct vaporflowing into said chamber from said conduit in heat transfer contactagainst said inclined surface and thereafter up said flue to enter saidinner compartment at said open top thereof.

9. A portable vacuum cooling plant comprising in combination: a hermeticenclosure having an access door and support means therein to receivepacked produce for treatment in said enclosure; a hermetically sealablechamber structurally separate from said enclosure and havingrefrigerating means to cool an interior surface thereof; a conduitinterconnected between said enclosure and chamber, said conduit having aquick-disconnect joint therein to permit physical removal of saidchamber from said enclosure; and a vacuum pump connected to said chamberto withdraw air therefrom whereby to cause air and vapor to dischargefrom said enclosure through said conduit into said chamber forcondensation of said vapor on said refrigerated surface.

10. The construction of claim 9 further characterized in that saidrefrigerating means includes a body of ice in said chamber.

11. The construction of claim 9 further characterized in that saidrefrigerating means includes a set of refrigerant circulating coilsinsaid chamber.

12. The construction of claim 9 further characterized in that saidrefrigerating means includes a heat transmitting portion in the wall ofsaid chamber and exterior bunker means to support ice against theexterior surface of said wall portion.

13. The construction of claim 9 further characterized by having a sumpsubstantially out of heat transfer relation With said chamber and meansinterconnecting said sump and chamber to drain condensate from saidchamber into said sump.

14. The construction of claim 9 further characterized in that said plantincludes a tractortrailer combination with said chamber mounted on saidtractor, and said enclosure mounted on said trailer.

15. In a portable vacuum cooling system of the class described: ahermetic enclosure having a sealable access door to receive material fortreatment in said enclosure; evacuation and condensation means includinga chamber having a cold surface therein, a vacuum pump connected to saidchamber to evacuate the same, and conduit means connected to saidenclosure to intercommunicate said chamber and enclosure, said conduitmeans including a quick-disconnect joint to permit physical separationof said enclosure and chamber; and means to direct liquid condensateforming on said cold surface to a point in said chamber adjacent theinflux of vapor and air from said conduit means whereby the air-vapormixture drawn from said enclosure through said chamber first passes inheat transfer relation past said condensate and then in contact withsaid cold surface.

MELVILLE W. BEARDSLEY.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 211,821 Wickes Jan. 28, 1879 222,122 Bate Dec. 2, 18791,458,403 Glessner June 12, 1923 2,345,548 Flosdorf Mar. 28, 19442,505,201 Peterson Apr. 25, 1950

